The invention relates to a method for operating an electrical steering system of an industrial truck which has a steering wheel and at least one steered wheel, wherein there is an assignment which assigns a target value for a rotational position of the steering wheel to each rotational position of the at least one steered wheel. With the method, a rotational movement of the steering wheel of the industrial truck is detected, and an electrical steering drive for the at least one steered wheel is actuated such that the detected rotational movement of the steering wheel is converted into a rotational movement of the at least one steered wheel according to a predetermined transmission factor. The invention also relates to an industrial truck intended for implementing the method.
With industrial trucks having a steering wheel and an electrical steering drive there is no direct mechanical connection between the steering wheel and the steered wheel. It is however desirable to have a fixed assignment between the rotational position of the steered wheel and the rotational position of the steering wheel, particularly for example, with straight-line travel in order to allow a preferred position of the steering wheel. Now, and in the following, the rotational position of the steered wheel is always considered to be the angular position relevant for the direction of travel, which is also called the steering angle.
The publication EP 1 310 419 A2 discloses different methods for aligning a steering angle sensor for an electrical steering system of an industrial truck. With the known methods, a distinction is made between an alignment phase and an operating phase of the industrial truck. The alignment phase is initiated when the industrial truck is restarted. In the alignment phase, the actual position of a steering angle sensor and the steered wheel is detected. The steering angle sensor is adjusted, without actuating the steered wheel, until it is determined that assuming a predetermined transmission ratio, a reference position of the steering angle sensor leads to a reference position of the steered wheel. Then, the operating phase is started during which actuation of the steered wheel takes place. In a variant of the known method, in the alignment phase the wheels are actuated according to a first transmission ratio until it is determined that the reference position of the steering angle sensor with a specific transmission ratio leads to the predefined position of the steered wheels, and then the operating phase is started which uses the specific transmission ratio.
Based upon this background, the object of the present invention is to provide a method for operating an electrical steering system of an industrial truck that guarantees a preferred rotational position of the steering wheel with specific steering angles, also during the ongoing operation of the industrial truck, and that can be implemented largely without the driver's knowledge, as well as an industrial truck provided for implementing the method.